Method and apparatus for reshaping cell-based traffic

ABSTRACT

A cell-based router comprising a controller to receive provisioning information including a transport rate of at least one frame-based router among a group of frame-based routers in a communication network, adjust cell transmission rate to avoid packet losses at the frame-based routers, where cell-based traffic is routed to a bidirectional cell and frame based switch according to updated bandwidth comprising the adjusted cell transmission rate, where the bidirectional cell and frame based switch is coupled to the cell-based router and the frame-based routers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/156,813 filed with the U.S. Patent and Trademark Office on Jun. 20,2005, now U.S. Pat. No. 7,660,312, the disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

This invention relates generally to content services, and moreparticularly to a method and apparatus for reshaping cell-based traffic.

BACKGROUND OF THE INVENTION

Historically, ATM (Asynchronous Transfer Mode) has been a cell-basedtransport protocol, without any significant knowledge or understandingof the underlying frame (also referred to as packet) structure that isbeing transmitted. Technology advances have taken a path whereby moreand more functions are being moved to frame-based services. The fixedlength cells that have made ATM such a deterministic transport are nowbecoming a liability with frame-based services and transports.

ATM has always had more overhead than most other protocols. Although theATM cell header is only 5 bytes, this overhead is imposed on each cell.Given that cells are only 53 bytes long, this amounts to almost 10%overhead. This fixed overhead is often referred to as a “cell tax”. Forlarge frames, 1000 bytes and more, this can amount to over a hundredbytes of cell headers. In addition, cells must be padded out to a totalof 48 payload bytes. While the overhead for large frames can be about10%, the real problems happen with small frames. Aside from the celltax, for small frames the required cell padding can account for as muchas 40% additional overhead. A 60 byte frame therefore requires 2 cellsworth of payload, with the second cell including 12 bytes of real dataand 36 bytes of padding.

Up until recently, normal traffic mixes would only generate a smallpercentage of these tiny data frames. However, the advent of Voice overIP (VoIP) is creating a substantial increase in packetized voice trafficand its resultant small frames. This becomes a problem when a cell-basedtransport is combined with a frame-based transport.

FR (Frame Relay) to ATM (FR/ATM) intercommunications is accomplished bylinking the virtual connections of a frame relay interface with that ofan ATM interface. Frame relay is a frame-based transport. Part of thefunction performed by the FR and ATM switches is the conversion of ATMcells to frames and frames to ATM cells. This function is dependent onthe definition of the virtual connection. Because ATM transport has moreoverhead than frame relay, the typical guidelines for creating an FR/ATMconnection is to provide more bandwidth on the ATM side of theconnection to account for this added overhead.

Historically, this asymmetry in FR/ATM provisioning has been based onthe generally acceptable mixtures of small, medium, and large dataframes as found on the Internet. Known as the IMIX (Internet MIXture),the resultant provisioning guidelines typically call for 12 to 18% extrabandwidth on the ATM side of the interface. These guidelines, whileappropriate for IMIX traffic, does not work well for traffic flows thatare mixed voice and data, or predominantly VoIP. VoIP traffic canrequire anywhere from 15 to 110% extra bandwidth on the ATM side of aFR/ATM connection. Although this can be a well defined quantity,depending upon the VoIP CODEC (Coder/Decoder) and sampling interval, anychange in these parameters can greatly impact the asymmetry percentage.Mixed voice and data traffic presents other problems that are also foundwith varying CODECs and sampling intervals.

The problem with mixed voice and data traffic is that on the frame relayside of the connection if there is insufficient ATM bandwidth it willnot be possible for the ATM network to generate the necessary number ofcells to carry the frames supplied by the frame relay network. This isespecially true for small frames that will generate a proportionallylarger number of cells greater than the ATM network can support. Theconverse is also true of large frames that are presented to the ATMnetwork. If the asymmetry percentage is too high and the ATM bandwidthis much larger than the frame relay bandwidth, large frames will bepackaged in cells with little overhead or padding. As these cells areconverted back to frames, there will be more frames generated than canbe handled by the frame relay network. Either of these scenarios canresult in data losses that can impact customer services. While it ispossible to optimize the FR/ATM interface for either large or smallframes, it is currently not possible to do both at the same time.

SUMMARY OF THE INVENTION

Embodiments in accordance with the invention provide a method andapparatus for reshaping cell-based traffic.

In one exemplary embodiment, a cell-based router can include acontroller to receive provisioning information including a transportrate of at least one frame-based router among a group of frame-basedrouters in a communication network, adjust cell transmission rate toavoid packet losses at the frame-based routers, where cell-based trafficis routed to a bidirectional cell and frame based switch according toupdated bandwidth comprising the adjusted cell transmission rate, wherethe bidirectional cell and frame based switch is coupled to thecell-based router and the frame-based routers.

In another exemplary embodiment, a switch can be operably coupled to aplurality of cell-based routers and a plurality of frame-based routers.The switch can include a controller to provide provisioning informationto a plurality of cell-based routers where the provisioning informationincludes a transport rate of at least one frame-based router among agroup of frame-based routers in a communication network, receivecell-based traffic from the plurality of cell-based routers according toan adjusted cell transmission rate where the adjusted cell transmissionrate is based on the provisioning information, and transmit thecell-based traffic to one or more of the frame-based routers.

In another exemplary embodiment, a method can include buffering datacells of one or more cell-based routers of a plurality of cell-basedrouters based on transport rates of a frame-based router where thecell-based routers and the frame-based router are coupled to abidirectional cell and frame based switch and where at least one of thecell-based routers is provisioned with the transport rate of theframe-based router, and routing cell-based traffic to the bidirectionalcell and frame based switch.

In yet another embodiment, a communication network can have a pluralityof cell-based routers, a plurality of frame-based routers, and abidirectional cell and frame based switch coupled to the cell-basedrouters, and frame-based routers. Each of the cell-based routers isprogrammed to reshape traffic bandwidth to avoid packet losses at theframe-based routers, and route cell-based traffic to the bidirectionalcell and frame based switch according to the updated bandwidth.

In yet another embodiment, a plurality of cell-based routers can becoupled to a bidirectional cell and frame based switch has a computerstorage medium having computer instructions for reshaping cell-basedtraffic bandwidth to avoid packet losses at frame-based routers coupledbidirectional cell and frame based switch, and routing cell-basedtraffic to the bidirectional cell and frame based switch according tothe updated bandwidth.

In yet another embodiment, a plurality of cell-based routers coupled toa bidirectional cell and frame based switch can operate according to amethod having the steps of reshaping cell-based traffic bandwidth toavoid packet losses at the frame-based routers coupled to thebidirectional cell and frame based switch, and routing cell-basedtraffic to the bidirectional cell and frame based switch according tothe updated bandwidth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of a hybrid cell and frame based communicationnetwork according to an embodiment of the present invention;

FIG. 2 depicts a flowchart of a method operating in the cell-basedrouters according to an embodiment of the present invention; and

FIG. 3 depicts a table illustrating the operation of the frame-based andcell-based routers according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims defining the features ofembodiments of the invention that are regarded as novel, it is believedthat the embodiments of the invention will be better understood from aconsideration of the following description in conjunction with thefigures, in which like reference numerals are carried forward.

FIG. 1 is block diagram of a hybrid cell and frame based communicationnetwork 100 according to an embodiment of the present invention. Asdepicted in FIG. 1, the communication network 100 comprises a cluster102 of cell-based routers 104 coupled to a bidirectional cell and framebased switch 110. The switch 110 is also coupled to a cluster 106 offrame-based routers 108. Cell-based routers 104 utilizes conventionaltechnology for routing, for example, ATM (Asynchronous Transfer Mode)traffic. A frame-base routers 108, on the other hand, utilizeconventional technology for routing frame (packet) traffic.

A conventional frame relay (FR) switch 114 is used for directing frametraffic to an ATM switch 112 which converts the frame-based traffic tocell-based traffic. The cell-based traffic is then supplied to thecell-based routers 104. In the reverse direction, the ATM switch 112accepts ATM traffic from the cell-based cluster 102 and directs thetraffic to the FR switch 114 for translation of cell-based traffic toframe-based traffic. Cell-based traffic operates according tofixed-sized frames, while frame-based traffic utilizes variable-sizedframes.

FIG. 3 depicts a table illustrating the operation of the frame-based andcell-based routers 104 and 108 according to an embodiment of the presentinvention. Scenarios 1 through 3 depict the issues with prior artsystems, while Scenario 4 illustrates a solution to said deficiencies inaccordance with the present invention.

Scenario 1 shows a case where the bandwidth of the ATM cluster 102 isincreased 13% above the data rate of a frame relay cluster 106. That is,at a frame relay rate of 1,536,000 bps (bits per second), there is a113% asymmetry between the FR and cell-based clusters 106 and 102,respectively, so as to produce an ATM data rate of 1,736,680 bps. Innetworks where VoIP is not prevalent, such an asymmetry may besufficient to support mostly data traffic. However, as VoIP trafficincreases, thereby generating a high volume of small frames, theasymmetry may not be sufficient.

In the present illustration, for example, VoIP traffic sourced by aconventional codec such as G.711 requires a data rate of 83,200 bps. Tosupport this rate, an ATM rate of 106,000 bps is needed. With 18simultaneous sessions (i.e., 18 simultaneous VoIP calls), the framerelay rate needs to be 1,497,600 bps (83,200*18), while the ATM raterequired is 1,908,000 (106,000*18). The FR rate is within the bounds ofits operating bandwidth (1,536,000 bps). The same cannot be said of theATM cluster 102. Thus, when VoIP traffic is high (such as in thisexample) the ATM cluster 102 cannot support the large number of smallframes sourced by the FR cluster 106 without data losses.

In the opposite direction (i.e., ATM to FR transition), 16 simultaneoussessions are supported on the ATM cluster 102. This translates to an ATMrate of 1,735,008 bps, and an FR rate of 1,331,200 bps, both of whichare within their operating capability. In the case of data transfersusing FTP (File Transfer Protocol) the ATM cluster 102 and FR cluster106 have no problem supporting bidirectional transfers.

Scenarios 2 and 3 illustrate what can happen when the asymmetry inbandwidth between the ATM cluster 102 and FR cluster 106 is increased toovercome the issues highlighted in scenario 1. At an asymmetry of 120%,the ATM cluster 102 can now process 18 simultaneous sessions of VoIPtraffic from the FR cluster 106. However, downstream FTP traffic becomesa problem for the FR cluster 106 for 131 simultaneous data sessions.Upon increasing the asymmetry to 150%, the ATM cluster 102 can continueto process 18 simultaneous sessions of VoIP traffic from the FR cluster106. However, downstream VoIP traffic and FTP traffic become a problemfor the FR cluster 106 at 17 and 131 simultaneous VoIP and datasessions, respectively.

To overcome these deficiencies in the art, each of the cell-basedrouters 104 are programmed according to a method 200 as depicted in FIG.2 in accordance with the present invention. Method 200 begins with step202, whereby each cell-based router 104 is provisioned with thetransport rates of at least one of the frame-based routers 108 of the FRcluster 106. The step of provisioning the cell-based routers 104 can bestatic or dynamic. That is, the cell-based routers 104 can beprovisioned once in a network 100 under an assumption that the FR to ATMasymmetries remain constant. Alternatively, where asymmetries can bevaried, the cell-based routers 104 can be provisioned periodically asnetwork adjustments take place.

Once provisioned, the cell-based router 104 proceeds to step 204 whereit reshapes traffic bandwidth according to the transport rates of theframe-based routers 108. Referring back to FIG. 3, the reader willrecall that in scenario 3, the downstream traffic from the ATM cluster102 to the FR cluster 106 was problematic. That is, the FR cluster 106was unable to process the ATM traffic for VoIP or FTP at an asymmetry of150%. With the present invention in accordance with step 204, thecell-based routers 104 are programmed to reshape their output bandwidthaccording to the traffic rate supported by the frame-based routers 108.Accordingly, a cell-based router will buffer data cells so as to adjustthe cell transmission rate in step 206 so that a frame relay ratesourced by the switch 110 is within the operating constraints of theframe-based routers 108. This is reflected in scenario 4 of FIG. 3,wherein the upstream and downstream FR rates are forced by thecell-based routers 104 to be identical and therein within the operatingrange of the FR cluster 106.

It should be evident by now that the present invention can be realizedin hardware, software, or a combination of hardware and software.Moreover, the present invention can be realized in a centralizedfashion, or in a distributed fashion where different elements are spreadacross several interconnected processors. Any kind of computer device orother apparatus adapted for carrying out method 200 described above issuitable for the present invention.

Additionally, the present invention can be embedded in a computerprogram product, which comprises all the features enabling theimplementation of method 200, and which when loaded in a computer systemis able to carry out these methods as computer instructions. A computerprogram in the present context means any expression, in any language,code or notation, of a set of instructions intended to cause a systemhaving an information processing capability to perform a particularfunction either directly or after either or both of the following: a)conversion to another language, code or notation; b) reproduction in adifferent material form.

It should be also evident from the embodiments that the presentinvention may be used for many applications. Thus, although thedescription is made for particular arrangements and methods, the intentand concept of the invention is suitable and applicable to otherarrangements and applications not described herein. It would be cleartherefore to those skilled in the art that modifications to thedisclosed embodiments described herein could be effected withoutdeparting from the spirit and scope of the invention.

In accordance with various embodiments of the present invention, themethods described herein are intended for operation as software programsrunning on a computer processor. Dedicated hardware implementationsincluding, but not limited to, application specific integrated circuits,programmable logic arrays and other hardware devices can likewise beconstructed to implement the methods described herein. Furthermore,alternative software implementations including, but not limited to,distributed processing or component/object distributed processing,parallel processing, or virtual machine processing can also beconstructed to implement the methods described herein.

It should also be noted that the software implementations of the presentinvention as described herein are optionally stored on a tangiblestorage medium, such as: a magnetic medium such as a disk or tape; amagneto-optical or optical medium such as a disk; or a solid statemedium such as a memory card or other package that houses one or moreread-only (non-volatile) memories, random access memories, otherre-writable (volatile) memories or Signals containing instructions. Adigital file attachment to e-mail or other self-contained informationarchive or set of archives sent through signals is considered adistribution medium equivalent to a tangible storage medium.Accordingly, the invention is considered to include a tangible storagemedium or distribution medium, as listed herein and includingart-recognized equivalents and successor media, in which the softwareimplementations herein are stored.

Although the present specification describes components and functionsimplemented in the embodiments with reference to particular standardsand protocols, the invention is not limited to such standards andprotocols. Each of the standards for Internet and other packet switchednetwork transmission (e.g., TCP/IP, UDP/IP, HTML, HTTP) representexamples of the state of the art. Such standards are periodicallysuperseded by faster or more efficient equivalents having essentiallythe same functions. Accordingly, replacement standards and protocolshaving the same functions are considered equivalents.

Accordingly, the described embodiments ought to be construed to bemerely illustrative of some of the more prominent features andapplications of the invention. It should also be understood that theclaims are intended to cover the structures described herein asperforming the recited function and not only structural equivalents.Therefore, equivalent structures that read on the description shouldalso be construed to be inclusive of the scope of the invention asdefined in the following claims. Thus, reference should be made to thefollowing claims, rather than to the foregoing specification, asindicating the scope of the invention.

What is claimed is:
 1. A network cluster comprising: a plurality ofcell-based routers in a communication network, each of the cell-basedrouters comprising: a memory storing computer instructions; and acontroller coupled to the memory, wherein the controller, responsive toexecuting the computer instructions, performs operations comprising:receiving provisioning information including an initial provisionedtransport rate based on a number of sessions of traffic that can beaccommodated within a non-congested operating range of a frame-basedrouter among a plurality of frame-based routers in the communicationnetwork; and adjusting a cell transmission rate, resulting in anadjusted cell transmission rate, according to the initial provisionedtransport rate prior to an occurrence of congestion of downstreamtraffic at the plurality of frame-based routers, wherein cell-basedtraffic is routed to a bidirectional cell and frame based switchaccording to updated bandwidth comprising the adjusted cell transmissionrate, and wherein the bidirectional cell and frame based switch iscoupled between the plurality of cell-based routers and the plurality offrame-based routers.
 2. The network cluster of claim 1, wherein the celltransmission rate is adjusted by buffering data cells.
 3. The networkcluster of claim 2, wherein provisioning is statically determined. 4.The network cluster of claim 2, wherein provisioning is dynamicallydetermined according to adjustments made to the initial provisionedtransport rate of the frame-based router.
 5. The network cluster ofclaim 2, wherein the cell transmission rate is adjusted so that a framerelay rate sourced by the switch remains within the non-congestedoperating range of the frame-based router.
 6. The network cluster ofclaim 1, wherein the bidirectional cell and frame based switchcomprises: an asynchronous transfer mode switch; and a frame relayswitch, wherein the asynchronous transfer mode switch and the framerelay switch are coupled, and wherein the asynchronous transfer modeswitch and the frame relay switch exchange the cell-based traffic andframe-based traffic.
 7. The network cluster of claim 1, wherein thecell-based traffic comprises fixed-sized frames, and wherein frame-basedtraffic comprises variable-sized frames.
 8. A switch operably coupled toa plurality of cell-based routers and a plurality of frame-basedrouters, the switch comprising: a memory storing computer instructions;and a controller coupled to the memory, wherein the controller,responsive to executing the computer instructions, performs operationscomprising: providing provisioning information to each cell-based routerof the plurality of cell-based routers, the provisioning informationincluding an initial provisioned transport rate of a frame-based routeramong the plurality of frame-based routers in a communication network,wherein the initial provisioned transport rate is based on a number ofsessions of traffic that can be accommodated within a non-congestedoperating range of the frame-based router; receiving cell-based trafficfrom the plurality of cell-based routers according to a celltransmission rate adjusted according to the initial provisionedtransport rate prior to an occurrence of congestion of downstreamtraffic at the plurality of frame-based routers; and transmitting thecell-based traffic to a frame-based router of the plurality offrame-based routers.
 9. The switch of claim 8, wherein the celltransmission rate is adjusted by buffering of data cells so that a framerelay rate sourced by the switch remains within the non-congestedoperating range of the frame-based router.
 10. The switch of claim 9,wherein provisioning of the initial provisioned transport rate isstatically determined.
 11. The switch of claim 9, wherein provisioningof the initial provisioned transport rate is dynamically determinedaccording to adjustments made to the initial provisioned transport rateof the frame-based router.
 12. The switch of claim 9, comprising: anasynchronous transfer mode switch; and a frame relay switch, wherein theasynchronous transfer mode switch and the frame relay switch arecoupled, and wherein the asynchronous transfer mode switch and the framerelay switch are configured to exchange cell-based and frame-basedtraffic.
 13. The switch of claim 12, wherein the cell-based trafficcomprises fixed-sized frames, and wherein frame-based traffic comprisesvariable-sized frames.
 14. A method comprising: provisioning acell-based router of a plurality of cell-based routers with an initialprovisioned transport rate of a frame-based router of a plurality offrame-based routers, wherein the initial provisioned transport rate isbased on a number of sessions that can be accommodated withinnon-congested operating ranges of the plurality of frame-based routers;and buffering data cells of each cell-based router of the plurality ofcell-based routers according to the initial provisioned transport rateof the frame-based router prior to an occurrence of congestion ofdownstream traffic at the plurality of frame-based routers, wherein theplurality of cell-based routers and the plurality of frame-based routersare coupled to a cell and frame based switch; and routing cell-basedtraffic to the cell and frame based switch.
 15. The method of claim 14,wherein provisioning the cell-based router of the plurality ofcell-based routers with the initial provisioned transport rate of theframe-based router of the plurality of frame-based routers is by thecell and frame based switch.
 16. The method of claim 15, whereinprovisioning is statically determined.
 17. The method of claim 15,wherein provisioning is dynamically determined according to adjustmentsmade to the initial provisioned transport rate of the frame-basedrouters.
 18. The method of claim 15, comprising adjusting a celltransmission rate by the buffering of the data cells so that a framerelay rate sourced by the cell and frame based switch remains within thenon-congested operating ranges of the frame-based router.
 19. The methodof claim 17, comprising adjusting a cell transmission rate by thebuffering of the data cells so that a frame relay rate sourced by thecell and frame based switch remains within the non-congested operatingranges of the frame-based router.
 20. The method of claim 14, whereinthe cell-based traffic comprises fixed-sized frames, and whereinframe-based traffic comprises variable-sized frames.